What is the efficacy of botulinum toxin (BTX) injections for the management of myofascial pain?

Updated: Jun 19, 2018
  • Author: Anthony H Wheeler, MD; Chief Editor: Meda Raghavendra (Raghu), MD  more...
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Several publications, including a case report and an open-label study involving 77 patients, have emphasized the benefit of BTX in the management of chronic myofascial pain. [55, 56, 57] One published review of BTX-A treatment for chronic musculoskeletal pain found no clinical evidence of its beneficial efficacy, despite scientific evidence of BTX analgesic qualities. [58]

Reports of the use of BTX for treatment of piriformis muscle syndrome included a randomized, controlled, crossover study of 9 patients who were treated with 100 U of either BTX-A or placebo using EMG and fluoroscopic guidance for injection placement. Childers and colleagues reported a trend toward greater pain relief for patients receiving toxin as opposed to placebo. [59] Fanucci and associates reported that 26 of 30 patients with piriformis syndrome who were injected with BTX-A under computerized axial tomographic guidance obtained relief of their symptoms within 5-7 days. [60]

Fishman et al performed 2 studies looking at BTX use for patients with piriformis syndrome. In one noncontrolled study, the authors concluded that BTX-A injections may be a useful adjunctive measure to physical therapy in the management of this syndrome. [52] In a follow-up dose-ranging study with BTX-B for piriformis syndrome using EMG guidance, Fishman reported that patients experienced notable symptom improvement. [61]

A double-blind, randomized, controlled study of BTX-A use for chronic myofascial pain compared 30 patients with trigger points in the infraspinatus muscle. Subjects were divided into a treatment group who received 50 U/0.25 mL saline or a placebo group who just received 0.25 mL of isotonic saline. Outcome measures included localized and referred pain, pain detection and tolerance thresholds to mechanical pressure (electronic algometer), and shoulder movement assessed at 3 and 28 days after injection. EMG interference patterns were evaluated at baseline and at 28 days following BTX-A injections. BTX-A significantly reduced motor endplate activity and EMG interference patterns; however, no significant differences were found in any of the outcome measures between groups.

BTX-A has antinociceptive and muscle-spasmolytic properties that may be hypothesized to alleviate signs and symptoms of myofascial pain syndromes (MPS). A prospective, double-blind 12-week, multicenter, randomized controlled trial by Gobel et al found that patients with upper-back MPS who received injections of 400 Ipsen units of BTX-A (Dysport) to 10 individual trigger points demonstrated significantly improved pain levels at 4-6 weeks after treatment without adverse side effects. [62]

Lew et al enrolled 29 study participants from 45 screened patients in a double-blind, randomized controlled trial to determine the efficacy of BTX-A in treating neck and upper-back pain of myofascial origin. [63] Study subjects received a one-time injection of either BTX-A or NS. Outcome measures included the VAS for pain, the Neck Disability Index (NDI), and the 36-item Short-Form Health Survey (SF-36).

Participants were evaluated at 2 weeks and at 1, 2, 3, 4, and 6 months. Improvements in the VAS and NDI scores were seen in both groups, but differences were not statistically significant between the treatment and comparison groups. However, statistically significant improvements were seen in the SF-36 bodily pain (at 2 mo and 4 mo) and mental health (at 1 mo) scales in the BTX-A treated group. Therefore, the authors could only surmise that trends towards improvement in the VAS and NDI scores did not show a BTX-A effect that could be differentiated from placebo effect; however, a larger study using the same or similar psychometric measures is warranted. No serious adverse events were reported.

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